Why not invert the Tubelab SE board?

[BillEpstein]

Searching the archives comes up with heat sinks as a reason not to invert the board and tube extenders as an alternative.

If the heat sinks and all other parts are"under" the board with it inverted, tube sockets "on top", what's the problem? What am I missing?

[wicked1]

Mine is inverted. You just have to be creative w/ mounting and cooling.
works great. I play mine almost 8 hours a day for years.

[wicked1]

Ive attached a pic..
the heatsink on the heater regulator worked fine when I was running the amp out in the air, but once I put it in its chassis, I had to greatly increase the size of that heat sink. I also put a small fan under the chassis to keep air circulating down there. I don't think the fan is necessary, but I had it, it's quiet, and I'm sure it helps.

Wow, looking at the picture I'm attaching, you can see the PCB is already discolored from heat near the heater regulator! that pic is years old, and before the amp was in it's chassis. I'm kind of afraid to look at the amp now!

-edit- yeah, currently my amp shows some serious signs of heat.. Don't know if it's bad or not.. But the plastic shrink wrapping on my angela re-branded caps has shrunken itself off, and the PCB near both sets of IC's (regulators and power drive) is badly discolored.

[tubelab.com]

what's the problem? What am I missing?

Wicked1 has just reported on the main reason. The mosfet heat sinks get hot. Heat rises. With the heat sinks under the board the heat rises into the PC board cooking it. The discoloration will not cause any problems other than minor ugliness. The long term heating and cooling can cause some solder joints to become brittle. It may be a good idea to resolder the connections in the area of the discoloration next time the amp is apart.

The filament regulator has 5 leads. There is no easy way to mount it on the bottom of the board without rebending the leads. I have broken a lead off of a chip doing this. As Wicked1 showed it is possible to hang the regulator off of the edge of the board. This still requires some minor lead bending.

I have built an amp with the tall parts on the back of the board and the filament regulator hanging off the edge. The regulator, the mosfets, and the CCS chips were all heat sinked to an aluminum plate under the PC board. This requires some creative blind assembly, but worked very well. I sold that amp almost 3 years ago and never saw it again, so I must assume it is still doing well.

Since then I have found it easier to use socket savers to raise the 9 pin tubes above the board. I used brass tubing extensions to elevate the 4 pin and octal tubes. All of the semiconductors were heat sinked to the aluminum chassis plates using angle aluminum and insulating washers. I haven't had the time to build any amplifiers in almost two years but I have a Tubelab SE almost finished that is being assembled in this manner. It is being photographed during assembly for posting to my web site.

[wicked1]

I used small jumper wires for the 5 pin regulator. Short as possible (as you can see, it's right at the edge of the board).

Also, the fan I put in the chassis is a p3 socket style fan. The way it sits, it sucks air past the regulator heatsinks, and blows it out the sides, which gets a little flow past the power drive/CCS chips.

[rknize]

I pretty much did the same thing way back in the beginning.





The FETs get very got like this. After designing the chassis, it became clear that I could top mount and still achieve the look I was going for.

Still a work in progress:

http://www.diyaudio.com/forums/tubes...orry-long.html